Synthesis and Crystal Structure of Ag₄I₄ Nanoclusters in the Sodalite Cavities of Fully K⁺-Exchanged Zeolite A

Ag 4 I 4 nanoclusters have been synthesized in half of the sodalite cavities of fully K + -exchanged zeolite A. An additional KI molecule is retained in each large cavity as part of a near square planar K 4 I 3+ cation. A single crystal of Ag 12 -A, prepared by the dynamic ion-exchange of Na 12 -A (LTA) with aqueous 0.05 M AgNO 3 and washed with CH 3 OH, was placed in a stream of flowing 0.05 M KI in CH 3 OH at 294 K for 2 days. The crystal structure of the product, K 9 Si 12 Al 12 O 48 ·(Ag 4 I 4 ) 0.5 ·K 4 I 3+, a = 12.290(1) Å, was determined by single-crystal X-ray diffraction in the cubic space group Pm 3̄ m. It was refined with all measured reflections to the final error index R 1 = 0.077 (based on the 264 reflections for which F o > 4σ( F o )). The thirteen K + ions per unit cell are found at three crystallographically distinct positions: eight K + ions in the large cavity fill the 6-ring site, three K + ions fill the 8-rings, and two K + ions are opposite 4-rings in the large cavity. One iodide ion per unit cell lies opposite a 4-ring in the large cavity, held there by two 8-ring and the two 6-ring K + ions (K 4 I 3+ ). Two Ag + and two I - ions per unit cell are found on 3-fold axes in the sodalite cavity, indicating the formation of Ag 4 I 4 clusters (interpenetrating tetrahedra; symmetry T d; diameter ca. 8.0 Å) in half of the sodalite units. Each cluster (Ag−I = 2.97(2) Å) is held in place by the coordination of its four Ag + ions to the zeolite framework (each Ag + cation is 2.48(1) Å from three 6-ring oxygens) and by the coordination of its four I - ions to large-cavity K + ions through 6-rings (I−K = 2.72(6) Å).